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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hello,<o:p></o:p></span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p>&nbsp;</o:p></span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>I am creating a new metric using CUDA implementation. So far
I found it is very difficult to get the derivative value from my
implementation. I&#8217;d like to know if there is an optimizer in ITK which is
derivative free. Or is there any other way to calculate the derivative value?<o:p></o:p></span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p>&nbsp;</o:p></span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks a lot!<o:p></o:p></span></font></p>

<p class=section1 style='margin:0cm;margin-bottom:.0001pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><o:p>&nbsp;</o:p></span></font></p>

<p class=section1 style='margin:0cm;margin-bottom:.0001pt'><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>Huanxiang Lu</span></font><o:p></o:p></p>

<p class=section1 style='margin:0cm;margin-bottom:.0001pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><o:p>&nbsp;</o:p></span></font></p>

<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p>&nbsp;</o:p></span></font></p>

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